High frequency signal transmission structure and method for same

ABSTRACT

A high frequency signal transmission structure includes an insulating sheet and a conductive wiring layer forming on the insulating sheet. The conductive wiring layer includes a silver conductive layer forming on the insulating sheet, a copper conductive layer forming on the silver conductive layer, and a silver covering layer covering a top surface and side surfaces of the copper conductive layer. The silver conductive layer and the silver covering layer together surround the copper conductive layer.

The subject matter herein generally relates to a multifunction sensingdevices.

BACKGROUND

Metal copper is generally used to manufacturing conductive wire layer.However, when the conductive wire layer is used to transmit a highfrequency signal, a large loss is generated.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations of the present technology will now be described, by wayof example only, with reference to the attached figures.

FIG. 1 is a flowchart of a method for manufacturing a high frequencysignal transmission structure in accordance with a first embodiment.

FIG. 2 is a diagrammatic view of an insulating sheet of the structure ofFIG. 1 in accordance with a first embodiment.

FIG. 3 is a diagrammatic view of a silver bottom layer formed on theinsulating sheet of FIG. 2.

FIG. 4 is a diagrammatic view of a dry film formed on the silver bottomlayer of FIG. 3.

FIG. 5 is a diagrammatic view of the dry film being exposed to alithographic method of FIG. 4.

FIG. 6 is a diagrammatic view of the dry film being developed through alithographic method of FIG. 5.

FIG. 7 is a diagrammatic view of forming of a copper conductive layer onthe silver bottom layer of FIG. 6.

FIG. 8 is a diagrammatic view showing removal of the dry film of FIG. 6.

FIG. 9 is a diagrammatic view showing the silver bottom layer is etchedto form a silver conductive layer on the insulating sheet.

FIG. 10 is a diagrammatic view of a silver covering layer being formedon the copper conductive layer of FIG. 8 to obtain a high frequencysignal transmission structure.

DETAILED DESCRIPTION

It will be appreciated that for simplicity and clarity of illustration,where appropriate, reference numerals have been repeated among thedifferent figures to indicate corresponding or analogous elements. Inaddition, numerous specific details are set forth in order to provide athorough understanding of the embodiments described herein. However, itwill be understood by those of ordinary skill in the art that theembodiments described herein can be practiced without these specificdetails. In other instances, methods, procedures, and components havenot been described in detail so as not to obscure the related relevantfeature being described. Also, the description is not to be consideredas limiting the scope of the embodiments described herein. The drawingsare not necessarily to scale and the proportions of certain parts may beexaggerated to better illustrate details and features of the presentdisclosure.

Several definitions that apply throughout this disclosure will now bepresented.

The term “substantially” is defined to be essentially conforming to theparticular dimension, shape, or other feature that the term modifies,such that the component need not be exact. For example, “substantiallycylindrical” means that the object resembles a cylinder, but can haveone or more deviations from a true cylinder. The term “comprising,” whenutilized, means “including, but not necessarily limited to”; itspecifically indicates open-ended inclusion or membership in theso-described combination, group, series, and the like. The references “aplurality of” and “a number of” mean “at least two.”

FIG. 10 illustrates a high frequency signal transmission structure 100according to a first embodiment. The high frequency signal transmissionstructure 100 includes an insulating sheet 10 and a conductive wiringlayer 40 formed on the insulating sheet 10.

A material of the insulation layer 10 is selected from the groupconsisting of polynaphthalene dicarboxylic acid glycol ester (PEN),polyimide (PI), and polyterephthalate (PET). The conductive wiring layer40 includes a silver conductive layer 22 formed on the insulating sheet10, a copper conductive layer 20 formed on the silver conductive layer22, and a silver covering layer 30 covering a top surface and sidesurfaces of the copper conductive layer 20. The copper conductive layer20 is sandwiched between the silver conductive layer 22 and the silvercovering layer 30. A thickness of the silver conductive layer 22 isabout 0.1˜2 nanometers. A thickness of the silver conductive layer 22 issame with a thickness of the silver covering layer 30.

An electrical conductivity of silver is about σ=6.17*10⁷ S/m, anelectrical conductivity of copper is about σ=5.80*10⁷ S/m. When the highfrequency signal transmission structure 100 is configured to transmit ahigh frequency signal, the current of the high frequency signal flowingthrough the conductive wiring layer 40 tends to be distributed on asurface of the conductive wiring layer 40 due to a conductor skineffect. And because the silver conductive layer 22 and the silvercovering layer 30 together surround the copper conductive layer 20, andthus the current tends to be distributed on a surface of the silverconductive layer 22 and the silver covering layer 30, and since anelectrical conductivity of silver is greater than an electricalconductivity of copper, transmission losses are reduced, and atransmission efficiency of the high frequency signal is improved.

FIG. 1 illustrates a flowchart in accordance with a second embodiment.The example method 200 for manufacturing the high frequency signaltransmission structure 100 (shown in FIG. 10) is provided by way of anexample, as there are a variety of ways to carry out the method.Additionally, the illustrated order of blocks is by example only and theorder of the blocks can change. The method 200 can begin at block 201.

At block 201, as shown in FIG. 2, an insulating sheet 10 is provided andis pre-treated using a plasma method to strength a silver bottom layer12 combine with the insulating sheet 10. The insulating sheet 10 is madefrom polyester polymer, thus the insulating sheet 10 comprised of estergroup (—COOR). In the illustrated embodiment, The pre-treatment methodincludes steps of first hydrolyzing ester group (—COOR) comprised in thepolyester polymer into carboxyl (—COOH), the carboxyl (—COOH) then beingchanged into ester (—COO⁻) in a slightly alkaline environment.

At block 202, as shown in FIG. 3, a silver bottom layer 12 is formed onthe insulating sheet 10 using a method of vacuum evaporation.Specifically, under a vacuum condition, the insulating sheet 10 is usedas a substrate, a metallic silver piece is arranged toward theinsulating sheet 10 as a target source. The target source is heated tounder a high temperature, the metallic silver piece evaporates to silverions, and the metal silver ions are gradually deposited on theinsulating substrate 10. Silver ions and ester group (—COO⁻) on asurface of the insulating sheet 10 form ionic bonds (—COO—Ag), and suchionic bonds can reach about 150-400 kJ/mole. The silver ions can thusadhere to the insulating sheet 10, and the silver bottom layer 12 isthus formed. The heating method can include resistance heating, electronbeam heating, laser beam heating, or plasma spray column heating.

At block 203, as shown in FIG. 4 to FIG. 7, a copper conductive layer 20is formed on the silver bottom layer 12. One portion of the silverbottom layer 12 is covered by the copper conductive layer 20, and theother portion is exposed by the copper conductive layer 20. In theillustrated embodiment, the copper conductive layer 20 is formed usingelectroplating method, rather than by a traditional wet etching process.Using an electroplating method to form the copper conductive layer 12reduces use of copper liquids, and is more environmentally friendly.

A method for forming the copper conductive layer 20 on the silver bottomlayer 12 comprises:

Firstly, as shown in FIG. 4, a dry film 14 is formed on the silverbottom layer 22.

Secondly, as shown in FIG. 5 and FIG. 6, the dry film 14 is exposedthrough a lithographic method to a pattern defined on the copperconductive layer 20. After the step of exposure and development, the dryfilm 14 then protects the silver bottom layer 12, and the portion of thesilver bottom layer 12 exposed by the dry film 14 can be electroplatedwith a layer of copper (see next step).

Thirdly, as shown in FIG. 7, a copper layer is electroplated onto thesilver bottom layer 12, and the layer of copper becomes the copperconductive layer 20, and one portion of the silver bottom layer 12 iscovered by the copper conductive layer 20.

Lastly, as shown in FIG. 8, the dry film 14 is removed, and the copperconductive layer 20 is in finished form on the silver bottom layer 12.

At block 204, as shown in FIG. 9, a fast vertical etching method is usedto remove the silver bottom layer 12 exposed by the copper conductivelayer 20. Only the silver bottom layer 12 sandwiched between theinsulating sheet 10 and the copper conductive layer 20 is retained. Thesilver bottom layer 12 sandwiched between the insulating sheet 10 andthe copper conductive layer 20 constitute the silver conductive layer22. In the illustrated embodiment, the silver bottom layer 12 is etchedusing an alkaline solution. Using an alkaline solution to fast-etch thesilver bottom layer 12 means that etching only takes place along adirection perpendicular to a surface of the insulating sheet 10. Anyetching which is done to a side of the copper conductive layer 20 can beignored, so the reliability of the copper conductive layer 20 is high,and cracks or breaks in the copper conductive layer 20 are reduced.

At block 205, as shown in FIG. 10, a silver covering layer 30 is formedon a top surface and side surfaces of the copper conductive layer 20.That is to say, the copper conductive layer 20 is sandwiched between thesilver covering layer 30 and the silver conductive layer 22. The silverconductive layer 22, the copper conductive layer 20 and the silvercovering layer 30 together form the conductive wiring layer 40.

The silver covering layer 30 is formed using a sterling silver method.That is to say, in a silver solution, silver ion in the silver solutionis replaced with copper comprised in the copper conductive layer 20,namely 2Ag⁺+Cu→2Ag+Cu²⁺. A silver covering layer 30 is gradually formedon the copper conductive layer 20, in this way, a thickness of theconductive wiring layer 40 can be better controlled. A high frequencysignal transmission structure 100 is thereby obtained.

The embodiments shown and described above are only examples. Therefore,many such details are neither shown nor described. Even though numerouscharacteristics and advantages of the present technology have been setforth in the foregoing description, together with details of thestructure and function of the present disclosure, the disclosure isillustrative only, and changes may be made in the detail, including inmatters of shape, size, and arrangement of the parts within theprinciples of the present disclosure, up to and including the fullextent established by the broad general meaning of the terms used in theclaims. It will therefore be appreciated that the embodiments describedabove may be modified within the scope of the claims.

What is claimed is:
 1. A method for manufacturing a high frequencysignal transmission structure, comprising: providing an insulatingsheet, evaporating a silver bottom layer on the insulating sheet;forming a copper conductive layer on part of the silver bottom layer;removing the silver bottom layer which exposed by the copper conductivelayer; and forming a silver covering layer on the copper conductivelayer, and the copper conductive layer is surrounded by the silverbottom layer and the silver covering layer, and the silver bottom layer,the copper conductive layer and the silver covering layer together forma conductive wiring layer.
 2. The method of claim 1, wherein theinsulating sheet is made from polyester polymer.
 3. The method of claim1, wherein before the step of evaporating a silver bottom layer on theinsulating sheet, further comprising a step of pre-treatment to thesurface of the insulating sheet.
 4. The method of claim 3, wherein amethod of the pre-treatment comprising: and the ester group comprised inthe insulating sheet is first hydrolyzed into carboxyl, the carboxyl(—COOH) then changed into ester ions (—COO⁻) in a slightly alkalineenvironment.
 5. The method of claim 2, wherein a method for forming thecopper conductive layer comprising: forming a dry film on the silverbottom layer; exposing and development the dry film to deform a patternof the copper conductive layer; electroplating a copper layer on thesilver bottom layer to form the copper conductive layer, and removingthe dry film.
 6. The method of claim 1, wherein the silver bottom layerof exposed by the copper conductive layer is removed by an etchingmethod using an alkaline solution.
 7. The method of claim 1, wherein athickness of the silver conductive layer is same with a thickness of thesilver covering layer.
 8. A high frequency signal transmission structurecomprising: an insulating sheet, and a conductive wiring layer formingon the insulating layer comprising: a silver conductive layer forming onthe insulating sheet, a copper conductive layer forming on the silverconductive layer, and a silver covering layer covering a top surface andside surfaces of the copper conductive layer, the silver conductivelayer and the silver covering layer together surround the copperconductive layer.
 9. The high frequency signal transmission structure ofclaim 8, wherein a thickness of the silver conductive layer is about0.1˜2 μm.
 10. The high frequency signal transmission structure of claim8, wherein the insulating sheet is made from polyester polymer.
 11. Thehigh frequency signal transmission structure of claim 8, wherein thesilver conductive layer is formed on the insulating sheet using vapordeposition method.
 12. The high frequency signal transmission structureof claim 8, wherein a thickness of the silver conductive layer is samewith a thickness of the silver covering layer.
 13. A method formanufacturing a high frequency signal transmission structure,comprising: providing an insulating sheet, forming a silver bottom layeron the insulating sheet; forming a copper conductive layer on a surfaceof the silver bottom layer; removing the silver bottom layer whichexposed by the copper conductive layer; and forming a silver coveringlayer on the copper conductive layer, and the copper conductive layer issurrounded by the silver bottom layer and the silver covering layer, andthe silver bottom layer, the copper conductive layer and the silvercovering layer together form a conductive wiring layer.
 14. The methodof claim 13, wherein the insulating sheet is made from polyesterpolymer.
 15. The method of claim 13, wherein before the step ofevaporating a silver bottom layer on the insulating sheet, furthercomprising a step of pre-treatment to the surface of the insulatingsheet.
 16. The method of claim 13, wherein a method of the pre-treatmentcomprising: and the ester group comprised in the insulating sheet isfirst hydrolyzed into carboxyl, the carboxyl (—COOH) then changed intoester ions (—COO⁻) in a slightly alkaline environment.
 17. The method ofclaim 13, wherein a method for forming the copper conductive layercomprising: forming a dry film on the silver bottom layer; exposing anddevelopment the dry film to deform a pattern of the copper conductivelayer; electroplating a copper layer on the silver bottom layer to formthe copper conductive layer, and removing the dry film.
 18. The methodof claim 13, wherein the silver bottom layer of exposed by the copperconductive layer is removed by an etching method using an alkalinesolution.
 19. The high frequency signal transmission structure of claim13, wherein the silver conductive layer is formed on the insulatingsheet using vapor deposition method.